Re: Hdpe wear strips
I see 2 possibilities:
1. Make the holes in the HDPE or UMHW oval in the first place and don't tighten down the bolts so much as to prevent the movement, and thereby allow the movement.
2. Steal a trick from the original railway rails - don't make the strip continuous the length of the boat. Cut it up into smaller strips with, say, an 1/8th of an inch gap between the ends, to allow the expansion longitudinally to take up with each smaller strip. It would still put some stress on the bolts and holes, but not as much on each bolt as with a continuous strip. An 1/8th inch gap shouldn't be enough to affect the function of the strip but if you are worried about stuff getting into the gap, you could half-lap the ends. At your stated expansion rate of 1" per 10' per 100 degrees, I reckon making each strip about a foot long, along with the aforementioned 1/8 gap, would take care of the problem
"A man who is not afraid of the sea will soon be drowned, for he will be going out on a day he shouldn't. We do be afraid of the sea, and we only be drowned now and again" Arran Islands Fisherman